1. Technical Field of the Invention
The present invention relates to high voltage rectifier devices, and more particularly to such devices which exhibit significantly lower forward conduction and switching losses than conventional devices.
2. Relevant Art
Bipolar rectifiers are conventionally used for high voltage applications (e.g., above 200–300V). These rectifiers are typically realized with a p-i-n structure in order to provide an adequate reverse breakdown capability. However, the intrinsic region must exhibit high resistivity for the device to function properly. This results in a high voltage drop in the forward conduction mode, and in many high current applications, is the main source of power losses.
In some cases rectifiers can be replaced with switches controlled with dedicated control circuitry. These rectifiers are called synchronous rectifier circuits and offer the advantage of reducing forward conduction losses and to provide fast switching, but this requires use of active circuitry to detect the required status and operate the switch itself.
One approach which has been tried in an effort to reduce forward resistance in high voltage switches is illustrated in U.S. Pat. No. 6,483,369 for COMPOSITE MOSFET CASCODE SWITCHES FOR POWER CONVERTERS. In the patented device, a composite structure is formed of a large die size high voltage MOSFET arranged in cascode with a low voltage small die size MOSFET for the purpose of improving efficiency and switching speed. However, this approach suffers from the disadvantage that it requires additional control circuitry to perform synchronous rectifier function.
Accordingly, there is still a need for a simple, low loss, fast switching rectifier device for use at high voltages.